The Research On Modeling Secondary Clarifiers In Wastewater Treatment Plant

In water and wastewater treatment plants as well as in a variety of industrial processes, secondary clarifiers are used to separate suspended solids from water. Additionally, the clarifier is also used to concentrate the settled sludge and recycle it to the biological reactor. Thus, the secondary clarifier forms a crucial component of treatment process. It is necessary to carry out researches on the operating regulations of the secondary clarifiers.First of all, a new type of model for describing the relationship between zone settling velocity (Vs) and stirred sludge volume index (SSVI) is developed. The applicability of the relationship was tested by analysing data published earlier in the literature. Based on these data it was found that the model can be used in wide ranges of SSVI and sludge concentration. And also, the new model have both advantages of the Vesilind model and the Tackacs model. However, more tests should be applied to confirm the validity of the new model.Secondly, in order to provide scientific basis for engineering design and control, and quest for a pattern of function of secondary clarifier, a new model for secondary clarifier is established. The new model quantitatively characterizes the biochemical phenomena in secondary clarifier with chemometrics methods, and further describes diversification of elements in the tank. The results show that the new model makes a more precise prediction on concentration of suspended sludge and truly characterizes ammonia nitrogen in activated sludge systems.Thirdly, via analysis of case, numerical simulation of secondary settling tank was performed through computational fluent dynamics (CFD) software, and the paper modified the structure of baffle in the tank. The conclusion suggested that the modification reduced the circulation and upgraded the capability of the tank. And also, the modification increased the water supply with lower cost. So the application of CFD software is efficient for the research on modifying the structure of secondary settling tanks.Finally, The equations governing unsteady flows in secondary settling tanks, a component of the wastewater treatment process, are analyzed using the finite element method. The model corresponding to such liquid-solid flows is highly nonlinear and...